• 한국해양공학회지
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• 제17권4호
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• pp.1-7
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• 2003

A virtual reality technology for multipurpose numerical simulation is developed to reproduce and investigate a variety of ocean environmental problems in a 3D Numerical Wave Tank(NWT). The governing equations for solving incompressible fluid motion are Navier-Stokes equation and continuity equation. The Marker-Density function technique is adopted to implement the fully nonlinear freesurface kinematic condition. The marine environmental situations, i.e., waves, currents, etc., are reproduced by use of multi-segmented wavemakers on the basis of the so-called ″snake-principle″. In this paper, some numerical reproduction techniques for regular, and irregular waves, multi-directional waves, Bull's-eye wave. wave-current, and solitary wave are presented, and a model test in motion with large amplitude of roll angle is conducted in the developed 3D-NWT, using a overlaid grid system.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.174-180
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• 2002

A virtual reality technology for multipurpose numerical simulation is developed to reproduce and investigate a variety of ocean environmental problems in a 3D-Numerical Wave Tank. The governing equations for solving incompressible fluid motion are Navier-Stokes equation and continuity equation, and the Marker-Density function technique is adopted to implement the fully-nonlinear free-surface kinematic condition. The marine environmental situations, i.e. waves, currents, wind, etc., are reproduced by use of multi-segmented wavemaker on the basis of the so-called "snake-principle". In this paper, some numerical reproduction techniques for regular and irregular waves, multi-directional waves, Bull's-eye wave, wave-current, and solitary wave are presented, and a model test in motion with large amplitude of roll angle is conducted in the developed 3D-NWT, using a overlaid grid system.

• 한국해양공학회지
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• 제20권4호
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• pp.83-90
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• 2006

Recently, as the technology of utilization for the ocean space is being advanced, floating structures are asked for being mare and mare huge-scale. A very large floating structure(VLFS) is considered as a flexible structure, because of a quite large length-to-breadth ratio and its geometrical flexibility. The main object of this study is to develop an accurate and convenient method on the hydroelastic response analysis of very large offshore structures on the real sea states. The numerical approach for the hydorelastic responses is based on the combination of the three dimensional source distribution methods, the dynamic response analysis method and the spectral analysis method. A model is considered as many rigid bodies connected elastic beam elements. The calculated results shaw good agreement with the experimental and calculated ones by Ohta.

• 한국해안·해양공학회논문집
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• 제27권4호
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• pp.238-245
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• 2015

Choi et al.(2015)은 최근 Boussinesq 방정식 모형인 FUNWAVE를 이용하여, 다방향 불규칙파 조건으로 SandyDuck 현장실험 조건의 연안흐름을 수치모의하여, 연안류 유속분포 뿐만 아니라 전단파동 등의 계산결과가 관측결과와 잘 일치함을 보였다. 이 연구모형을 기반으로 SandyDuck 지형과 더불어 다방향 위상의 상호작용에 의해 발생되는 연안방향의 파에너지 비균등성이 이안류 발달에 미치는 영향을 고찰하기 위해 수치모의를 수행하였다. 이 결과 지형에 의해 발생하는 이안류가 지배적인 규칙파 조건과 달리 다방향 불규칙파 위상의 상호작용에 따른 돌발적 이안류의 발생이 추가되어 매우 복잡한 쇄파대의 연안 순환흐름을 재현함을 알 수 있었다.

• 한국연안방재학회지
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• 제4권1호
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• pp.1-6
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• 2017

Most of the short period waves are blocked by the breakwaters when the short period irregular waves propagate into the ports. However, nonlinear irregular wave numerical experiments show that the long waves generated by the nonlinear interaction is predominant in the port. Seiches phenomenon in Geumjin Fishing Port is very similar to 60 and 300 second harbor oscillations. By arranging the inner breakwater of the proper length in the inside of the port, it is possible to effectively reduce seiches, as well as the short-period wave, and significantly improve the harbor tranquility. In the case of rectangular basin type such as the Geumjin Fishing Port, the multi-directional irregular wave numerical model should be used for the investigation and countermeasures for the harbor tranquility.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.303-308
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• 2004

The failure at the head section of rubble mound breakwaters is more important than other failure modes. because this initial failures will occur the failure of the trunk section and lead to the instability of the structure. The three-dimensional failure modes are discussed using the experimental data with multi-directional waves considering the failure modes. It was occurred by the topographical characteristics around the head of rubble mound breakwater. The spacial characteristics of failure mode around the rubble-mound structures can be summarized as follows: 1) It was clarified that the failure modes at the round head of a detached breakwater are classified as failure by plunging breaker on the slope, failure by direct incident wave force and failure at the rubble mound breakwaters. 2) The failure mode was found in the lower wave height than the design wave by the breaker depth effects and topography around structures. It is clarified that the structure was monitored safely designed for the design wave but the failure was occurred by the reason of breaker waves.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2010년도 정기 학술발표대회
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• pp.66.2-66.2
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• 2010

장대 케이슨 방파제에 작용하는 다방향 불규칙파랑의 파력 평활화 계수를 계산하였다. 다방향 불규칙파랑의 주파수 스펙트럼으로는 Bretschneider-Mitsuyasu 스펙트럼을 사용하였고, 방향 스펙트럼은 Mitsuyasyu 타입의 스펙트럼을 적용하였다. 계산 결과 단일 케이슨의 길이가 길수록, 주파향의 입사각이 클수록 평활화 계수는 감소하였다. 다양한 에 대해서도 계산하였으며, 가 클수록 평활화계수는 규칙파와 비슷한 경향을 보였다.

• 동력기계공학회지
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• 제9권3호
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• pp.26-32
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• 2005

The volumetric efficiency is significantly affected by the behavior of pressure wave in induction system and exhaust pipe. By the motion of the piston, there exist pressure fluctuation in induction system which produce waves. Waves are propagated along a pipe bi-directional as they propagated through it, making compression wave and rare-faction(expansion) wave. These wave phenomena can affect to the volumetric efficiency. As a method of improvement of the volumetric efficiency, fuel economy and pollutant emission reduction particularly in low engine speeds, a side-branch additional tunable helmholtz resonator on the secondary pipe of intake system is proposed by use of their acoustic vibrations. Some of results are presented which deal with their physical phenomena for the wave action of intake system in a four-stroke three cylinders diesel engine.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.317-322
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• 2003

The Sectional and Spatial failure modes are discussed using the experimental data with long crest wave and multi-directional waves considering the failure modes occurring around the rubble-mound breakwater. The spatial & sectional stability and failure mode around the rubble-mound structures with construction progress can be summarized as follows: 1) The rubble mound structures at basic construction step was occurred serious failures when ${\xi}$ was about 6.5. 2) It was clarified that the failure modes at the round head of detached breakwater are classified as failure by plunging breaking on the slope, failure by direct incident wave force and failure by scouring at the toe of the detached break water. 3) The failure mode was found in the lower wave height than the design wave by the breaker depth effect. 4) The failure on the slope were also developed at the lee side of the round head because diffracted wave propagated into the behind area by grouping effect of multi-directional irregular wave.

• 한국해안·해양공학회논문집
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• 제27권6호
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• pp.424-433
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• 2015

본 연구에서는 회절을 고려하여 반무한방파제 형식의 직립식 장대구조물에 작용하는 파력에 대해 검토하였다. 장대구조물에 작용하는 파력은 규칙파, 일방향 불규칙파 및 다방향 불규칙파를 대상으로 하였다. 방파제 전면 및 후면에서 발생하는 회절을 모두 고려하였다. 방파제의 상대길이(1/L)가 0인 경우 방파제에 작용하는 파력은 회절에 의해 0이 된다. 방파제의 상대길이가 1.0 이하인 경우에는 회절의 영향이 비교적 강하였으며, 방파제의 상대길이가 0.5 이상인 경우에는 방파제의 장대화 효과에 의해 작용 파력이 크게 감소하였다. 즉, 방파제의 상대길이가 1.0 이하인 경우에는 회절효과의 고려가 필요하며, 장대 방파제의 파력 감소효과를 얻기 위해서는 방파제의 상대길이가 최소 0.5 이상이어야 함을 알 수 있다.